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Biomedical subjects

J G Porterfield

Publications and source records attributed to J G Porterfield.

At least 19 recordsLinked to original sources
PubMed1997

Daily variations in the occurrence of symptomatic supraventricular tachycardia as determined by ambulatory event monitoring.

The diurnal incidence of supraventricular tachycardia (SVT), including atrial fibrillation and atrial flutter, has been quantified by examining 7,891 cases of symptomatic arrhythmia in 5,869 patients assigned to ambulatory monitoring using electrocardiographic event recorders with transtelephonic reporting. The probability of occurrence of SVT was found to be high and moderately variable throughout the normally active hours of the day between 8 A.M. and 8 P.M. and to be uniformly low during the inactive hours between 1 and 5 A.M. Age-related peaks within the active phase were independently associated with the older half of the study population (9 A.M.) and with the younger half (6 P.M.). The daily incidence of SVT is primarily characterized by 2 states of activity, active and quiescent. Quiescence of SVT is associated with normal sleep and inactivity.

Adult↗
PubMed1996

Compatibility of a nonthoracotomy lead system with a biphasic implantable cardioverter-defibrillator. Cadence-Endotak 60-Series IDE investigators.

This prospective multicenter study was conducted under the Food and Drug Administration Investigational Device Exemption to evaluate the safety and efficacy of the combination of the Cadence implantable defibrillator (Ventritex, Inc.) and 60-series Endotak C leads (Cardiac Pacemakers, Inc.). Implantation was attempted in 148 patients with hemodynamically compromising ventricular tachycardia or fibrillation (VF), or with pace-terminable ventricular tachycardia. The system was successfully implanted in 97% of patients, with 96% of implants in a transvenous-lead-alone configuration. At implantation, the defibrillation threshold was 455 +/- 94 V (14 +/- 6 J) for lead-alone patients and 532 +/- 40 V (19 +/- 3 J) for those requiring a subcutaneous patch. VF conversion efficacy was reconfirmed in patients who underwent a 3-month chronic induction study. The system successfully detected all 763 induced arrhythmias and terminated 99.5% of them; after system modification, successful conversion was demonstrated in the 2 patients who initially had induced episodes requiring external defibrillation (1 lead revision; 1 reprogramming). All spontaneous episodes were terminated with an implantable-cardioverter defibrillator. Postshock VF redetection times were significantly shorter than initial detection times (4.5 +/- 1.8 seconds detection, 2.1 +/- 0.7 seconds redetection; p<0.0001). During an 8-month mean follow-up (range 1 to 31 months), 2 unwitnessed deaths were classified as sudden cardiac deaths, and 11 patients experienced a total of 12 complications, none of which was associated with the Cadence-Endotak combination.

Adult↗
PubMed1996

The shocking lung mass: a case report.

Two years after implantation of an ICD with epicardial patch leads, a patient presented with hemoptysis. The posterior left ventricular patch was found to have eroded into lingular segmental bronchus. During thoracotomy, the hardware was removed and the bronchus successfully repaired.

Aged↗
PubMed1994

A new approach: a single triple electrode lead system interfaced with a third generation defibrillator.

The efficacy of implantable third generation cardioverter defibrillators has been well established for the treatment of patients with malignant ventricular arrhythmias and survivors of cardiac arrest. However, many patients have been reluctant or unwilling to endure the discomfort of an open chest procedure, despite their need for the device. Furthermore, morbidity (pneumothorax, pneumonia, sepsis, pleural effusion, hemorrhage, pericarditis, etc.) and mortality associated with the application of epicardial lead systems is of concern. Finally, the mean overall expense of $80,433 for the epicardial method of defibrillator implantation is a consideration in an era of increasing cost-awareness in health care. Fortunately, the recent market-release of a single lead transvenous defibrillation system [Endotak, Cardiac Pacemakers, Inc. (CPI), St. Paul, Minnesota] may address these pressing issues. The specific purpose of this report is to demonstrate the patient benefit derived from interfacing a single endocardial lead system with a biphasic third generation defibrillator.

Defibrillators, Implantable↗
PubMed1993

Experience with three different third-generation cardioverter-defibrillators in patients with coronary artery disease or cardiomyopathy.

Clinical investigations are being performed in multiprogrammable devices whose therapeutic options include antitachycardia pacing, cardioversion, defibrillation and bradycardia pacing. Three different third-generation devices were implanted in 46 research patients at 1 clinical center to document their safety and efficacy for the treatment of malignant ventricular arrhythmias. Additionally, the purpose of the study was to determine if antitachycardia pacing is a desirable and frequently used feature of tiered devices. The Medtronic PCD was implanted in 15 patients (12 men, mean age 60 +/- 13 years, mean ejection fraction 40 +/- 15%), the Ventritex Cadence in 21 patients (17 men, mean age 65 +/- 10 years, mean ejection fraction 38 +/- 12%), and the CPI VENTAK PRx in 10 patients (8 men, mean age 63 +/- 14 years, mean ejection fraction 31 +/- 8%). All patients presented with cardiac arrest or ventricular tachycardia. During follow-up of 10 +/- 6 months (range 1 to 19), 70% of the 20 patients with antitachycardia pacing activated used the feature for spontaneous ventricular tachycardia. The antitachycardia pacing parameters were reprogrammed 20 times in 15 patients. Two thousand six hundred thirty-eight of 2,675 (98%) antitachycardia pacing attempts successfully terminated spontaneous tachyarrhythmias. Low-energy cardioversion or defibrillation terminated tachyarrhythmias in patients where pacing was unsuccessful. One hundred forty-eight episodes of tachycardia were successfully treated directly by shocks in 16 of 46 patients (35%). There were no deaths due to device failure. This initial single-center clinical experience suggests that the PCD, Cadence and VENTAK PRx are all safe and effective tiered therapy devices for the treatment of malignant ventricular arrhythmias. Antitachycardia pacing successfully terminated most episodes of ventricular tachycardia; in patients with this feature activated, it was used frequently but required reprogramming to achieve high levels of success.

Aged↗
PubMed1993

Conversion rates of induced versus spontaneous ventricular tachycardia by a third generation cardioverter defibrillator. The VENTAK PRx Phase I Investigators.

Seventy consecutive patients received the first VENTAK PRx pulse generators (Cardiac Pacemakers, Inc.) implanted in the United States. This multiprogrammable device has therapeutic options that include: (1) antitachycardia pacing; (2) low energy cardioversion; (3) defibrillation shocks; and (4) bradycardia pacing. There were 60 males and 10 females with a mean age of 65.3 +/- 9.4 years. The anatomical diagnoses were coronary artery disease in 55 patients, cardiomyopathy in 7 patients, congenital heart disease in 2 patients, and miscellaneous disease in the remaining 6 patients. Thirty-six percent had a history of sudden cardiac death and 90% had documented monomorphic ventricular tachycardia. The mean ejection fraction was 32.7% +/- 12.2%. Thirty-three (49.3%) had an ejection fraction < or = 30%. Electrophysiological testing was done preimplant, predischarge, and 1 to 2 months postimplant to define a specific electrical therapy and evaluate the efficacy of the device. Two hundred ninety-three of 367 (80%) episodes of induced ventricular tachycardia were successfully terminated by the VENTAK PRx programmed for antitachycardia pacing. There were 1,794 total therapy episodes for spontaneous ventricular tachycardia; 91% (1,641 episodes) were terminated by antitachycardia pacing and 153 episodes were converted by shocks during a minimal 6-month follow-up per patient. We conclude that documentation of a successful antitachycardia pacing modality in the electrophysiology laboratory predicts conversion of spontaneous episodes of ventricular tachycardia. Furthermore, antitachycardia pacing by the VENTAK PRx can terminate the majority of episodes of ventricular tachycardia.

Aged↗
PubMed1991

Ninety-six episodes of spontaneous ventricular tachycardia in 1 week: success of ramp pacing by a pacer-cardioverter-defibrillator.

This case report describes the flexibility and usefulness of a pacer-cardioverter-defibrillator for the management of a 63-year-old patient with malignant ventricular tachyarrhythmias. Ninety of 96 episodes of ventricular tachycardia were terminated successfully with ramp pacing in a 1-week period. In those patients who have frequent episodes of ventricular tachycardia that respond to antitachycardia pacing, the multifunction device can add to the patient's comfort and increase acceptance of this type of device.

Cardiac Pacing, Artificial↗
PubMed1991

Long-term community hospital experience with the internal defibrillator.

Seventy-seven patients with drug refractory ventricular tachycardia (57) and ventricular fibrillation (20) received the implantable defibrillator. There were 55 men and 22 women with a mean age of 63 +/- 10 years. The anatomical diagnoses were coronary artery disease in 61 patients, cardiomyopathy in 15 patients, and aortic stenosis in one patient. The mean ejection fraction was 32 +/- 12%. Concurrent surgery at defibrillator implantation was coronary bypass in eight patients and aortic valve replacement in one patient. There were no intraoperative mortalities. The mean ventricular fibrillation termination threshold was 13 +/- 6 joules. During a follow-up period of 16 +/- 10 months (range 2-40 months) four patients died: electrical mechanical dissociation (two patients), respiratory failure, and sepsis. Thirty-eight patients (51%) continued receiving antiarrhythmic drug therapy, with quinidine sulfate and procainamide being the most frequently utilized agents. Fifty-four patients (72%) have received a mean of 9 +/- 10 shocks (range 1-44). Implantable defibrillators are often needed in patients seen in large community hospitals. This technology can be administered successfully in this setting with complications and results comparable to those reported from university hospitals. Implantable defibrillators are effective in preventing arrhythmic death and can be used with low risk to the patients.

Anti-Arrhythmia Agents↗
PubMed1991

A prospective study utilizing a transtelephonic electrocardiographic transmission program to manage patients in the first several months post-ICD implant.

We prospectively enrolled 20 consecutive patients (11 men and 9 women; mean age 63 +/- 9.5 years) post-AICD implant in a transtelephonic electrocardiographic transmission (TET) program. The monitor was chosen for its retrograde (30 seconds) and antegrade memory capabilities (45 seconds). The patients were discharged from the hospital after receiving instructions to utilize the system for any cardiac symptoms. The monitor was worn 1-3 months (mean 2.5 +/- 0.7 months). During the follow-up period there were 54 TETs received. Nine were for documented AICD discharges, 19 were for symptoms associated with arrhythmias (11 of these 19 reported AICD discharges that were not documented), and 26 for symptoms not associated with arrhythmias. Eight of the 9 AICD discharges documented were appropriate for ventricular tachycardia (mean 185 +/- 40 beats/min). The arrhythmias associated with symptoms were: atrial fibrillation (12); nonsustained ventricular tachycardia (3); ventricular couplets (2); ventricular premature beats (10); and atrial premature contractions (2). Several TETs documented multiple arrhythmias. The most common symptoms not associated with arrhythmias were shortness of breath, dizziness, chest pain, and nervousness. Office interrogation of the AICDs revealed 12 of the 20 patients (60%) had received AICD discharges, with 5 of these 12 patients unaware of this occurring. We found the TET monitoring system a useful tool in the management of the AICD patient the first several months postoperatively. We were able to assess device function and avoid unnecessary office visits and/or hospitalizations.

Atrial Fibrillation↗